No abstract

To help ban the use of general toxic algicides, research efforts are now directed towards the discovery of compounds that are specifically acting as cyanocides. Here, we review the past and look forward into the future, where the less desirable general algicides like copper sulphate, diuron or endothall may become replaced by compounds that show better specificity for cyanobacteria and are biodegradable or transform into non-toxic products after application. For a range of products, we review the activity, the mode of action, effectiveness, durability, toxicity towards non-target species, plus costs involved, and discuss the experience with and prospects for small water volume interventions up to the mitigation of entire lakes; we arrive at recommendations for a series of natural products and extracted organic compounds or derived synthetic homologues with promising cyanocidal properties, and briefly mention emerging nanoparticle applications. Finally, we detail on the recently introduced application of hydrogen peroxide for the selective killing of cyanobacteria in freshwater lakes.

International audienceThe aim of this paper was to summarize the current knowledge on how physical methods can reduce or control internal P release from sediments in lakes and reservoirs. Particular emphasis is given to the role of internal phosphorus load in fueling cyanobacterial blooms which are predicted to increase in frequency and intensity in response to climate change and eutrophication. We present selective case studies (both successful and unsuccessful) to assess the applicability and efficiency of major physical approaches used for decades to reduce internal loading in different systems of various morphology. In particular, we concentrate on where and when (1) hypolimnetic aeration/oxygenation, (2) hypolimnetic withdrawal and (3) sediment dredging are likely to reduce cyanobacterial blooms and whether these methods have an adverse impact on other organisms. We conclude that each method has its strength and weakness depending on the system considered. Sufficient knowledge of all lake nutrient sources and their dynamics together with detailed lake and sediment characteristics is an essential prerequisite for choosing an appropriate control method. We also report that many experiences demonstrated that a combination of restoration methods is often more successful than a single method. © 2015, Springer Science+Business Media Dordrecht

Cyanobacteria pose a serious threat to water resources around the world. This is compounded by the fact that they are extremely resilient, having evolved numerous protective mechanisms to ensure their dominant position in their ecosystem. We show that treatment with nanoparticles of zerovalent iron (nZVI) is an effective and environmentally benign method for destroying and preventing the formation of cyanobacterial water blooms. The nanoparticles have multiple modes of action, including the removal of bioavailable phosphorus, the destruction of cyanobacterial cells, and the immobilization of microcystins, preventing their release into the water column. Ecotoxicological experiments showed that nZVI is a highly selective agent, having an EC(50) of 50 mg/L against cyanobacteria; this is 20-100 times lower than its EC(50) for algae, daphnids, water plants, and fishes. The primary product of nZVI treatment is nontoxic and highly aggregated Fe(OH)(3), which promotes flocculation and gradual settling of the decomposed cyanobacterial biomass.

There are several green methods available to synthesize iron-based nanoparticles using different bio-based reducing agents. Although their useful properties in degradation of organic dyes, chlorinated organics, or arsenic have been described earlier, their characterization has been ambiguous, and further research is needed in this area. Synthesis and characterization details on iron-based nanoparticles produced by green tea extract are described in detail; characterization was carried out by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and UV−vis spectrometry followed by ecotoxicological assay. XRD and TEM analyses revealed that iron forms amorphous nanosized particles with size depending on reaction time. Moreover, low-temperature Mossbauer spectroscopy confirmed progressive reduction of Fe 3+ to Fe 2+ during the reaction. Finally, the iron(II,III) nanoparticles prepared by green tea extract (GT−Fe nanoparticles) were found to have negative ecotoxicological impacts on important aquatic organisms such as cyanobacterium (Synechococcus nidulans), alga (Pseudokirchneriella subcapitata), and even invertebrate organisms (Daphnia magna). The EC 50 values are 6.1 ± 0.5 (72 h), 7.4 ± 1.6 (72 h), and 21.9 ± 4.3 (24 h) mg of Fe per L, respectively.

No abstract

No abstract

Humans are exposed to phthalates released from plastics, cosmetics, or food on a daily basis. Phthalates have low acute liver toxicity, but their chronic exposures could induce molecular and cellular effects linked to adverse health outcomes, such as liver tumor promotion or chronic liver diseases. The alternation of gap junctional intercellular communication (GJIC) and MAPK-Erk1/2 pathways in liver progenitor or oval cells can disrupt liver tissue homeostatic mechanisms and affect the development and severity of these adverse outcomes. Our study with 20 different phthalates revealed their structurally dependent effects on liver GJIC and MAPK-Erk1/2 signaling in rat liver WB-F344 cell line with characteristics of liver oval cells. The phthalates with a medium-length side chain (3–6 C) were the most potent dysregulators of GJIC and activators of MAPK-Erk1/2. The effects occurred rapidly, suggesting the activation of non-genomic (non-transcriptional) mechanisms directly by the parental compounds. Short-chain phthalates (1–2 C) did not dysregulate GJIC even after longer exposures and did not activate MAPK-Erk1/2. Longer chain (≥7 C) phthalates, such as DEHP or DINP, moderately activated MAPK-Erk1/2, but inhibited GJIC only after prolonged exposures (>12 h), suggesting that GJIC dysregulation occurs via genomic mechanisms, or (bio)transformation. Overall, medium-chain phthalates rapidly affected the key tissue homeostatic mechanisms in the liver oval cell population via non-genomic pathways, which might contribute to the development of chronic liver toxicity and diseases.